docs: def subtract_column_median(df, prefix='Intensity '):
      """
      Apply column-wise normalisation to expression columns.
  
      Default is median transform to expression columns beginning with Intensity
  
  
      :param df:
      :param prefix: The column prefix for expression columns
      :return:
      """
      df = df.copy()
  
      df.replace([np.inf, -np.inf], np.nan, inplace=True)
  
      mask = [l.startswith(prefix) for l in df.columns.values]
      df.iloc[:, mask] = df.iloc[:, mask] - df.iloc[:, mask].median(axis=0)
  
      return df